TMR magnetic sensor

Abstract

The application provides a TMR magnetic sensor, which comprises: a first bridge arm coupled between a power supply end and an output end; a second bridge arm coupled between the output end and a ground end; one of the first bridge arm and the second bridge arm is a resistance whose resistance value changes with a magnetic field, and the other is a resistance whose resistance value does not change with the magnetic field; the first bridge arm and the second bridge arm are formed on the same substrate; the resistance whose resistance value changes with the magnetic field comprises a plurality of magnetic tunnel junctions; when a current flows through the resistance whose resistance value changes with the magnetic field, the flowing direction of the current in the junction region of the magnetic tunnel junction is perpendicular to the surface of the substrate; and when the current flows through the resistance whose resistance value does not change with the magnetic field, the flowing direction of the current is parallel to the surface of the substrate. In this way, the TMR magnetic sensor can be realized by one-time annealing, and single-chip integration of the bridge arm in the TMR magnetic sensor is not necessary, so that the difficulty of manufacturing the TMR magnetic sensor is reduced.

Description

Technical field

[0001] The present invention relates to the field of magnetic sensors, and in particular to a TMR (Tunnel Magneto-resistance, TMR) sensor. [Background Technology]

[0002] Existing TMR magnetic sensors generally use a Wheatstone full bridge or a Wheatstone half bridge to convert magnetic signals into voltage signals. Figure 1 The circuit structure diagram of the Wheatstone full-bridge TMR magnetic sensor includes four bridge arms 110, 120, 130, and 140 coupled between the first output terminal V+, the second output terminal V-, the power supply terminal VDD, and the ground terminal GND. The specific connection relationship is as follows: Figure 1 In the initial state of the TMR magnetic sensor, the angle between the magnetization directions of the free layer and the pinned layer of each bridge arm is ideally 90 degrees. Since the resistance of the bridge arm is related to this angle, when the angle is zero, the resistance of the bridge arm is minimum, and when the angle is 180 degrees, the resistance of the bridge arm is maximum. A full bridge requires that the resistance changes of two adjacent bridge arms are opposite. For example, when a rightward magnetic field is applied, the resistance of bridge arms 110 and 130 decreases, while the resistance of bridge arms 120 and 140 increases. This requires that the magnetization direction of the pinned layer of bridge arms 110 and 130 be opposite to that of the pinned layer of bridge arms 120 and 140.

[0003] In order to achieve opposite magnetization directions of the pinned layers of the two bridge arms on the same half bridge, there are generally several ways to achieve it. One is to use wire bonding, which can mechanically rotate one bridge arm in each half bridge by 180 degrees, and then connect the two bridge arms by wire bonding. However, this wire bonding method cannot achieve single-chip integration. The second is to use local annealing, that is, to use laser or other methods for local heating, and apply magnetic fields of different directions to different areas. This method requires multiple annealing methods, which is inefficient and costly. Annealing can increase the TMR value of the magnesium oxide barrier magnetic tunnel junction and define the magnetization direction of the pinned layer; the third is to set the initial direction of the magnetic moment of the pinned layer and the free layer to 45 degrees or 135 degrees. Compared with the initial angle of 90 degrees between the pinned layer and the free layer, the range is reduced. If a single chip is to be implemented as follows Figure 1 The structure shown has only local annealing.

[0004] In addition to full-bridge TMR magnetic sensors, there are also half-bridge or single-arm bridge TMR magnetic sensors. Figure 2 Schematic diagram of the circuit structure of a single-arm bridge TMR magnetic sensor 200a. Figure 3This is a schematic diagram of the circuit structure of a Wheatstone half-bridge TMR magnetic sensor 200b. The pinned layers of bridge arms 201 and 202 of TMR magnetic sensor 200a have the same magnetization direction. The resistance of bridge arm 201 varies with the magnetic field, while the resistance of bridge arm 202 does not. The pinned layers of bridge arms 203, 206, 204, and 205 of TMR magnetic sensor 200b have the same magnetization direction. The resistance of bridge arms 203 and 206 varies with the magnetic field, while the resistance of bridge arms 204 and 205 does not. In conventional methods, the thin films and processed structures of bridge arms 202, 204, and 205 have current flowing perpendicular to the film surface, similar to the structure of bridge arms 201, 203, and 205. However, thicker soft magnetic material must be prepared on or below bridge arms 202, 204, and 205 to shield the external magnetic field. This requires additional processing steps, increasing costs.

[0005] Therefore, it is urgent to propose a new technical solution to solve the above problems. [Summary of the invention]

[0006] One of the objectives of the present invention is to provide a TMR magnetic sensor that can achieve single-chip integration without using soft magnetic materials to shield the bridge arms in the TMR magnetic sensor, thereby reducing the difficulty of the TMR magnetic sensor manufacturing process.

[0007] To achieve the above objectives, according to one aspect of the present invention, a TMR magnetic sensor is provided, comprising: a power supply terminal, a ground terminal, and an output terminal; a first bridge arm coupled between the power supply terminal and the output terminal; and a second bridge arm coupled between the output terminal and the ground terminal; wherein one of the first bridge arm and the second bridge arm is a resistor whose resistance varies with a magnetic field, and the other of the first bridge arm and the second bridge arm is a resistor whose resistance does not vary with a magnetic field; the first bridge arm and the second bridge arm are formed on the same substrate; the resistor whose resistance varies with a magnetic field comprises a plurality of magnetic tunnel junctions, each magnetic tunnel junction comprising a top electrode region, a junction region coupled to the top electrode region, and a bottom electrode region coupled to the junction region; when current flows through the resistor whose resistance varies with a magnetic field, the current flows in a direction perpendicular to the surface of the substrate in the junction region; and when current flows through the resistor whose resistance does not vary with a magnetic field, the current flows in a direction parallel to the surface of the substrate.

[0008] Compared with the prior art, the present invention has one or more of the following advantages: the TMR magnetic sensor can be integrated into a single chip at low cost; a bridge-type TMR magnetic sensor can be realized by a single annealing method, without the need to use soft magnetic materials to shield the bridge arms in the bridge, thereby reducing the difficulty of the process manufacturing of the TMR magnetic sensor.

Brief Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0010] Figure 1 It is a schematic diagram of the structure of the Wheatstone full-bridge TMR magnetic sensor;

[0011] Figure 2 FIG1 is a schematic diagram of the circuit structure of a single-arm bridge-type TMR magnetic sensor in one embodiment;

[0012] Figure 3 FIG1 is a schematic diagram of the circuit structure of a Wheatstone half-bridge TMR magnetic sensor in one embodiment;

[0013] Figure 4 Schematic diagram of a top view of a resistor whose resistance value varies with a magnetic field in a TMR magnetic sensor of the present invention;

[0014] Figure 5 Schematic diagram of the cross-sectional structure of a resistor whose resistance value changes with the magnetic field in the TMR magnetic sensor of the present invention;

[0015] Figure 6 FIG1 is a schematic diagram of a top view of a resistor in a TMR magnetic sensor of the present invention, wherein the resistor does not change with the magnetic field;

[0016] Figure 7 Schematic diagram of the cross-sectional structure of a resistor in the TMR magnetic sensor of the present invention whose resistance does not change with the magnetic field;

[0017] Figure 8 FIG. 1 is a schematic top view of the structure of another embodiment of a resistor in the TMR magnetic sensor of the present invention whose resistance does not change with the magnetic field. [Specific implementation method]

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to separate or selective embodiments that are mutually exclusive of other embodiments. Unless otherwise specified, the terms "connected," "connected," and "connected" herein, indicating electrical connection, refer to direct or indirect electrical connection.

[0020] In the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "coupled" and the like should be understood in a broad sense; for example, it can be directly connected, or indirectly connected through an intermediate medium, which can be electronic components, functional circuits, etc. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0021] Figure 2 It is a schematic diagram of the circuit structure of a single-arm bridge TMR magnetic sensor 200a in an embodiment. As shown, the TMR magnetic sensor 200a includes a power supply end VDD, a ground end GND, an output end Output, a first bridge arm 201 coupled between the power supply end VDD and the output end Output, and a second bridge arm 202 coupled between the output end Output and the ground end GND. Figure 2

[0022] In the embodiment shown in Figure 2 , the first bridge arm 201 is a resistance whose resistance value changes with the magnetic field, and the second bridge arm 202 is a resistance whose resistance value does not change with the magnetic field. In another alternative embodiment, the first bridge arm 201 can also be a resistance whose resistance value does not change with the magnetic field, and the second bridge arm 202 can be a resistance whose resistance value changes with the magnetic field. That is, one of the first bridge arm 201 and the second bridge arm 202 is a resistance whose resistance value changes with the magnetic field, and the other of the first bridge arm 201 and the second bridge arm 202 is a resistance whose resistance value does not change with the magnetic field. The first bridge arm 201 and the second bridge arm 202 are formed on the same substrate, and the resistance whose resistance value changes with the magnetic field (such as the first bridge arm 201) and the resistance whose resistance value does not change with the magnetic field (such as the second bridge arm 202) both include a pinned layer formed at the same time, and the magnetization direction of the pinned layer of the resistance whose resistance value changes with the magnetic field (the direction of the black arrow in Figure 2 ) is the same as the magnetization direction of the pinned layer of the resistance whose resistance value does not change with the magnetic field.

[0023] Figure 3 It is a schematic diagram of the circuit structure of a Wheatstone half-bridge TMR magnetic sensor 200b in an embodiment. The TMR magnetic sensor 200b includes a power supply end VDD, a ground end GND, a first output end V+, a second output end V-, a first bridge arm 203 coupled between the power supply end VDD and the first output end V+, a second bridge arm 204 coupled between the first output end V+ and the ground end GND, a third bridge arm 205 coupled between the power supply end VDD and the second output end V-, and a fourth bridge arm 206 coupled between the second output end V- and the ground end GND.

[0024] In the embodiment shown in Figure 3 ​In the illustrated embodiment, the first bridge arm 203 and the fourth bridge arm 206 are both resistors whose resistance varies with the magnetic field, and the second bridge arm 204 and the third bridge arm 205 are both resistors whose resistance does not vary with the magnetic field. In another alternative embodiment, the first bridge arm 203 and the fourth bridge arm 206 are both resistors whose resistance does not vary with the magnetic field, and the second bridge arm 204 and the third bridge arm 205 are both resistors whose resistance varies with the magnetic field. In other words, the first bridge arm 203 and the fourth bridge arm 206 are either resistors whose resistance varies with the magnetic field or resistors whose resistance does not vary with the magnetic field, and the second bridge arm 204 and the third bridge arm 205 are either resistors whose resistance does not vary with the magnetic field or resistors whose resistance varies with the magnetic field.

[0025] The first bridge arm 203, the second bridge arm 204, the third bridge arm 205 and the fourth bridge arm 206 are formed on the same substrate. The resistors whose resistance varies with the magnetic field (such as the first bridge arm 203 and the fourth bridge arm 206) and the resistors whose resistance does not vary with the magnetic field (such as the second bridge arm 204 and the third bridge arm 205) all include pinned layers formed at the same time. The magnetization direction ( Figure 3 The direction of the black arrow in the figure is the same as the magnetization direction of the pinned layer of the resistor whose resistance does not change with the magnetic field.

[0026] Figure 4 Schematic diagram of a top view of the structure of resistors (such as bridge arms 201, 203, and 206) whose resistance varies with the magnetic field in the TMR magnetic sensors 200a and 200b of the present invention; Figure 5 Schematic diagram of the cross-sectional structure of resistors (such as bridge arms 201 , 203 , and 206 ) whose resistance varies with the magnetic field in the TMR magnetic sensors 200 a and 200 b of the present invention.

[0027] like Figure 4 and 5 As shown, the resistor whose resistance value changes with the magnetic field includes multiple magnetic tunnel junctions (MTJ) 310. Each magnetic tunnel junction 310 includes a top electrode region 301, a junction region 302 coupled to the top electrode region 301, and a bottom electrode region 303 coupled to the junction region 302. At least some of the magnetic tunnel junctions 310 are connected in series with each other, and the top electrode regions 301 or bottom electrode regions 303 of two adjacent magnetic tunnel junctions are connected, and the layer to which the top electrode region 301 belongs is located above the layer to which the junction region 302 belongs, and the layer to which the junction region 302 belongs is located above the layer to which the bottom electrode region 303 belongs. Figure 5As shown in the figure, the dotted line is the direction of current flow. When the current flows through the resistor whose resistance changes with the magnetic field, the current flow direction in the top electrode region 301 and the bottom electrode region 303 is perpendicular to the magnetization direction of the pinned layer and parallel to the surface of the substrate (the surface defined by the x-axis and the y-axis). The current flow direction in the junction region 302 is perpendicular to the surface of the substrate, that is, it flows along the z-axis direction, which will show a large TMR value. The bridge arms 201, 203, and 206 can all adopt Figure 4 and 5 The structure shown in FIG. It should be noted that the layer to which the junction region belongs is a tunneling layer, the layer to which the top electrode belongs can be a free layer or a pinned layer, and the layer to which the bottom electrode region belongs can also be a pinned layer or a free layer. That is, when the layer to which the top electrode belongs is a free layer, the layer to which the bottom electrode region belongs is a pinned layer; when the layer to which the top electrode belongs is a pinned layer, the layer to which the bottom electrode region belongs is a free layer.

[0028] Figure 6 2 is a schematic diagram of a top view of a resistor (such as bridge arms 202, 204, and 205) in a TMR magnetic sensor of the present invention, the resistance of which does not change with the magnetic field, in one embodiment; Figure 7 Schematic diagram of the cross-sectional structure of a resistor in the TMR magnetic sensor of the present invention whose resistance does not change with the magnetic field. Figure 8 FIG. 1 is a schematic top view of the structure of another embodiment of a resistor in the TMR magnetic sensor of the present invention whose resistance does not change with the magnetic field.

[0029] like Figure 6 and 8 As shown, the magnetization direction of the pinned layer is shown by the black arrow, and the resistor whose resistance does not change with the magnetic field includes a resistor strip arranged in a zigzag manner. Figure 7 As shown, the resistor strip includes a conformal top electrode region 401, a junction region 402 and a bottom electrode region 403. The top electrode region, the junction region and the bottom electrode region in the resistor whose resistance does not change with the magnetic field are located in the same layer as the top electrode region, the junction region and the bottom electrode region in the resistor whose resistance changes with the magnetic field. The black dotted arrow indicates the direction of current flow. When current flows through the resistor whose resistance does not change with the magnetic field, the current flows along the direction in which the resistor strip extends. The direction of current flow is parallel to the surface of the substrate. At this time, the TMR value is very small, and it can be regarded that the resistance basically does not change with the magnetic field. The bridge arms 202, 204, and 205 can all be used Figure 6-8 The structure shown.

[0030] like Figure 6 and 8 As shown, the resistor strips are arranged in a circuitous manner. The resistor strips include a plurality of parallel strip body portions 405 and a strip bending portion 406 connecting two adjacent strip body portions. The extension direction of the strip body portion 405 can be the same as the magnetization direction (x-axis) of the pinned layer. Figure 6 and Figure 8 The extension direction of the strip body portion 405 may also be perpendicular to the magnetization direction of the pinned layer, such as Figure 8 In other embodiments, the resistor strips may be arranged in other shapes, such as curved strips.

[0031] In the present invention, the TMR thin film layers of the bridge arms that vary with and do not vary with the magnetic field are identical, and can be fabricated using a single annealing process, eliminating the need for additional structures and processes. This allows single-arm bridge-type TMR magnetic sensors 200a and Wheatstone half-bridge TMR magnetic sensors 200b to be integrated on a single chip. Furthermore, the bridge-type TMR magnetic sensor can be fabricated using a single annealing process, eliminating the need for shielding the bridge arms with soft magnetic materials and reducing the manufacturing complexity of the TMR magnetic sensor.

[0032] A bridge-type TMR magnetic sensor fabricated on a semiconductor substrate or a thermally oxidized substrate exhibits a high TMR value when the current in the magnetic tunnel junction (MTJ) flows perpendicular to the membrane surface (CPP). When the current flows in-plane, the TMR value is very small. The structure of the present invention employs a bridge-arm output or half-bridge output mode. One arm utilizes a series-connected magnetic tunnel junction with current flowing perpendicular to the membrane surface. This arm exhibits a large TMR ratio, meaning that the resistance varies significantly with the magnetic field. The other arm utilizes a resistive strip structure with current flowing in-plane. This arm exhibits a very low TMR value, meaning that the resistance is essentially unchanged with the magnetic field. By connecting these two arms in a suitable manner, a voltage output of the bridge-type TMR magnetic sensor can be achieved.

[0033] In this article, "resistance does not change with magnetic field" does not simply mean that resistance does not change at all with magnetic field, but that resistance fluctuations with magnetic field are negligible.

[0034] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0035] Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention, and that those skilled in the art may make changes, modifications and variations to the above embodiments within the scope of the present invention.

Claims

1. A TMR magnetic sensor, characterized in that: It includes: Power supply terminal, ground terminal and output terminal; a first bridge arm coupled between the power supply terminal and the output terminal; a second bridge arm coupled between the output terminal and the ground terminal; One of the first bridge arm and the second bridge arm is a resistor whose resistance varies with the magnetic field, the other of the first bridge arm and the second bridge arm is a resistor whose resistance does not vary with the magnetic field, and the first bridge arm and the second bridge arm are formed on the same substrate. The resistor whose resistance varies with a magnetic field includes a plurality of magnetic tunnel junctions, each magnetic tunnel junction including a top electrode region, a junction region coupled to the top electrode region, and a bottom electrode region coupled to the junction region, and when current flows through the resistor whose resistance varies with a magnetic field, the current flows in the junction region in a direction perpendicular to the surface of the substrate; When current flows through the resistor whose resistance does not change with the magnetic field, the direction of current flow is parallel to the surface of the substrate.

2. The TMR magnetic sensor according to claim 1, wherein There are two output terminals, namely a first output terminal and a second output terminal. The first bridge arm is coupled between the power supply terminal and the first output terminal, the second bridge arm is coupled between the first output terminal and the ground terminal, and the TMR magnetic sensor further includes: a third bridge arm coupled between the power terminal and the second output terminal; a fourth bridge arm coupled between the second output terminal and the ground terminal; One of the third bridge arm and the fourth bridge arm is a resistor whose resistance changes with the magnetic field, and the other of the third bridge arm and the fourth bridge arm is a resistor whose resistance does not change with the magnetic field. The first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm are formed on the same substrate.

3. The TMR magnetic sensor according to claim 2, wherein: The first bridge arm and the fourth bridge arm are both resistors whose resistance varies with the magnetic field or resistors whose resistance does not vary with the magnetic field, and the second bridge arm and the third bridge arm are both resistors whose resistance does not vary with the magnetic field or resistors whose resistance varies with the magnetic field.

4. The TMR magnetic sensor according to any one of claims 1 to 3, wherein: The resistor whose resistance changes with the magnetic field and the resistor whose resistance does not change with the magnetic field both include pinned layers formed at the same time, and the magnetization direction of the pinned layer of the resistor whose resistance changes with the magnetic field is the same as the magnetization direction of the pinned layer of the resistor whose resistance does not change with the magnetic field.

5. The TMR magnetic sensor according to claim 4, wherein: At least some of the magnetic tunnel junctions in the resistor whose resistance changes with the magnetic field are connected in series with each other, and the top electrode regions or bottom electrode regions of two adjacent magnetic tunnel junctions are connected, the layer to which the top electrode region belongs is located above the layer to which the junction region belongs, and the layer to which the junction region belongs is located above the layer to which the bottom electrode region belongs, and the flow direction of the current in the top electrode region and the bottom electrode region is perpendicular to the magnetization direction of the pinned layer and parallel to the surface of the substrate, the layer to which the junction region belongs is a tunneling layer, the layer to which the top electrode region belongs is a free layer or a pinned layer, and the layer to which the bottom electrode region belongs is a pinned layer or a free layer.

6. The TMR magnetic sensor according to claim 5, wherein: The resistor whose resistance does not change with the magnetic field includes a resistor strip arranged in a zigzag manner, wherein the resistor strip includes a conformal top electrode region, a junction region, and a bottom electrode region, wherein the top electrode region, the junction region, and the bottom electrode region of the resistor whose resistance does not change with the magnetic field are respectively located in the same layer as the top electrode region, the junction region, and the bottom electrode region of the resistor whose resistance changes with the magnetic field. When current flows through the resistor whose resistance does not change with the magnetic field, the current flows along the direction in which the resistor strip extends and is parallel to the surface of the substrate.

7. The TMR magnetic sensor according to claim 6, wherein: The resistor bars are arranged in a circuitous manner and include a plurality of parallel bar main bodies and a bar bending portion connecting two adjacent bar main bodies.

8. The TMR magnetic sensor according to claim 7, wherein: An extending direction of the stripe main body is the same as or perpendicular to a magnetization direction of the pinned layer.

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